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Animal Navigation Introduction One of the most remarkable features of many non-human animal species is their ability to navigate over vast distances. Examples of this animal-Olympic ability include homing pigeons which can cover over 600 miles in one day (a feat Virgin rail can only dream about!) and the albatross that migrates over 4000 miles. The Arctic tern accomplishes a particularly impressive feat, although it does leave you wondering what the point is; it spends 2 weeks at the North Pole, a few weeks at the South Pole and the rest of the year flying between the two! Navigation over such vast differences may be for one of two main reasons; homing or for the purposes of migration. Questions on this topic will not specify which. Typical wording would be ‘discuss research studies into homing and/or migration in non-human species.’ This is fortunate because the two are difficult to disentangle. Surely if an animal migrates then on the return journey it is using similar skills and techniques in order to get home! However, I shall briefly look at the reasons for homing and migration before considering the techniques that may be used. Homing The texts say little about this other than stating the obvious, i.e. that it is the ability to find ones way home! There are clear advantages of being able to do this. If a species has to go out looking for food or mates then it needs to be able to find its way back to its burrow, nest etc. where presumably it is safer. If young are involved then it is essential that food can be taken back for them etc. The most famous species for its homing ability has to be the ‘homing pigeon’ but others include the salmon, purple martin and African antelope. Migration The reasons for this are not always so obvious but the texts have far more to say on the issue. Migration refers to the seasonal movement of some species which appears to be triggered by environmental factors such as temperature. Remember that migration is seen as a circannual rhythm. There are several advantages to migrating including warmer weather and avoiding severely cold weather at the poles, new feeding grounds or watering holes, possibility of finding new mates or sometimes avoiding predators. All of these are clearly advantageous to a species and increase its chances of survival or reproduction. However, migration comes at a cost. Vast amounts of energy can be consumed and there may be many dangers, such as predators, on the way. Fisher (1979) reported the death of at least 3,200 birds in one night in Illinois. The birds had flown into radio masts and similar tall structures!
Birds We normally associate migration with bird species. It is unusual for birds to migrate in one stage, preferring to break the journey down into smaller stages en route. Migratory journeys by birds appear to be a combination of innate and learned skills and this is best illustrated using the example of Perdeck’s starlings (1958). The starlings migrate in autumn from their breeding grounds in Russia to northern France, a south westerly journey. Perdeck intercepted some of the starlings en route in the Netherlands and took them south to Switzerland. Some birds were experienced others novices on their first migration. Perdeck found that when the birds were released to continue their journey that the young birds continued flying in a south westerly direction which brought them out in northern Spain, well south of where they should have been. However, the experienced birds (no rude comments), with the benefit of past migrations behind them, were able to adjust for the displacement and still find their way to north France. Perdeck concluded that the young birds were relying on innate skills whilst the mature birds were able to combine innate skills with learning from previous experience. Helbig (1991) in a bizarre but ingenious experiment showed the importance of innate factors. He took two related species of black cap, one of which migrated south east and the other south west. When these were cross bred their offspring, (you guessed it) flew south! Migration in the European stork also appears to be innate. Regardless of where the storks originate they all migrate to the same area of north Africa. Storks in Eastern Europe set out in an easterly direction and go via the Middle East. Storks in Western Europe set out in a south westerly direction and fly across the Mediterranean at Gibralter. Schuz (1971) took eggs of the east European species and transferred them to nests in the west. When they migrated they flew in an easterly direction just like their biological parents.
Fish and sea creatures Just as birds may use air currents such as thermals to help migrate then many sea species use underwater currents such as the Gulf Stream to cover vast distances. The loggerhead turtle is one such example. Navigation beneath the sea can be more problematic, for example it is more difficult to use sun, moon and stars. Some research suggests that it may be possible, for example loggerhead turtles in captivity swim towards light sources, but generally it is assumed that their vision is not good enough to make this a reliable method of navigation. Salmon are probably the fish most famed for its homing instinct. Here smell seems to play an important role in finding natal streams (streams where they were born). More detail about this later.
So having considered two reasons for why a species may need to navigate over long distances we will now consider how they achieve this feat. This is the most likely area to be examined!
Methods of navigation The simplest method of navigation is leaving a trail that can be retraced, like Daedulus in the Minotaur’s Labrynth (for classical scholars). The loris (a type of lemur apparently), uses ‘urine washing’ in which they pee on their hands and then rub the urine onto their feet to leave a scent trail. Try it the next time you’re out! Slightly more complex is piloting in which landmarks are remembered en route. These may be visual or olfactory but this method is only useful over short distances. Navigation by direction is the most complex and involves the use of sun, moon, stars and magnetic fields to orientate yourself in relation to your destination. In the following section I shall only consider the last two options.
Piloting or navigation by location can use either visual landmarks or smells. Landmarks Tinbergen & Kruyt (1938). If you’ve already revised animal memory you’ll be familiar with this one. This is still a classic experiment and needs to be treated as a key study. The researchers placed pine cones outside the nests of digger wasps, a species that lives in the ground. When the wasps leave the nest they orientate themselves by circling over the entrance to the nest and noting the position of landmarks, in this case the strategically placed pine cones. The researchers then move the cones a few metres away but keeping the same pattern. On their return the wasps still try to locate the entrance to the nest in the centre of the pine cones. As mentioned in memory notes, the researchers ruled out the possibility of smell being used by using a combination of scented pine cones and scented plates. Extension material but good for evaluation marks (AO2): Beusekom (1948) carried out a variation on the study placing pine cones in a circle around the entrance to the nest. When the cones were moved they were placed either in a circle, an ellipse or a square. They found that the wasps would try to find the entrance in the circle and the ellipse (a similar shape) but not in the square. In behaviourist terms the wasps had generalised the initial learning to an ellipse (just as Little Albert generalised from white rabbit to cotton wool etc), however they were able to discriminate between circle and square. Clearly landmarks are of limited use and are only suitable for navigation over short distances. It was once thought that racing or homing pigeons could find their way home by following landmarks remembered when they were being transported on their outward journey. Walcott & Schmidt-Koenig (1973) showed that this could not be the case by anaesthetising the birds during transportation! It is now thought that pigeons use a variety of methods for long distance navigation and only rely on landmarks for the last bit of the journey and locating the precise loft. (See notes on cognitive maps in ‘animal memory’ if you require further evidence).
Cartwright & Collett (1983) trained gerbils to find sunflower seeds and bees to find sugar solution. They arranged the food so that it was always a fixed distance and direction from a 40cm high cylinder. If the position of the cylinder was moved then this confused the creatures who would search in the wrong place suggesting:
However, the two species seemed to be using different techniques. When the height of the cylinder was altered the bees were confused. The researchers concluded that bees were using the size of the retinal image to locate position. However, height of the cylinder made no difference to the gerbils’ ability to find the food. Cartwright & Collett believed that the gerbils were using dead reckoning.
Dead reckoning This is the ability to know your location in respect to the target location in terms of the distance and direction moved away from it. Even when animals have taken a circuitous route away from the location they can still take the shortest route back. This is like you going to Leicester via Northampton and Coventry but coming back straight down the A6!
Olfactory maps As already mentioned the salmon appears to navigate its final stage of the journey home using smell. Much of the research on smell has been carried out by the Italian Papi. He believes pigeons build up a map of their location based on smell (olfactory map). Pigeons have been denied their sense of smell by a variety of methods, e.g. cutting their olfactory nerve, local anaesthetic or bunging wax up their nostrils! This does appear to disorientate them. However, it could be the pain and discomfort of the methods used that causes the problem. Strangely this disorientation only seems to occurr in Italy. It has been suggested that pigeons here rely on smell more because they tend to be kept in lofts high up on roof tops. In Frankfurt birds kept at ground level and deprived of smell are able to home okay. This suggests that the way birds are reared does affect their navigational abilities.
In more ethical follow up studies the wind has been scented. The wind blowing from the south is made to smell of olive oil (told you he was Italian) and the wind blowing from the north is made to smell of turpentine (perhaps he used to be a decorator). Pigeons then had drops of either olive oil or turps placed on their nostrils and they flew in the direction that they associated with that smell. However, there are few problems with this study, firstly it is thought pigeons have a poor sense of smell and it is not easy to replicate due to weather conditions. Honey bees also use smell to locate their own hive. Bees entering the wrong hive can cause ‘civil unrest’ with host bees fighting off the aliens.
Fishy smells Experiments have been carried out on salmon returning to their natal stream. Hasler (1986) found that plugging the nostrils of a salmon prevented it from accurately locating its own stream. Grier & Burk (1992) exposed young salmon to either one of two artificial smells in Lake Michigan. On their return to the lake they entered the stream matching that smell on 90% of occasions. It is not clear what smell the salmon are responding to under natural conditions. It could be a case of imprinting on the characteristic smell of that particular stream at a very young age or a response to pheromones released by their relatives. The most likely answer is both.
Navigation by direction This is the more sophisticated method of navigation and is necessary for homing or migrating over long distances. Possible methods available to species include use of sun, moon and stars and magnetic fields. Sun Humans have navigated using the sun for thousands of years and on clear days, even without any complex equipment it is possible to find directions from the position of the sun (east to west) in the sky. However, in order to do this we also need to know the time of day. For example we know that at midday, in the northern hemisphere, the sun is in the south and so on… Obviously we use clocks (the clock sold by Del Boy that made him a millionaire, was designed for navigational purposes at sea!), other species rely on their body clocks. Research evidence Bellrose (1958) noted that on clear days (when the sun is visible) mallards take off and immediately start heading in the right direction. However, on overcast days they appear disorientated at the start and fly randomly before finding their bearings.
Duck: happy Duck: sad
Santschi (1911) used mirrors to reflect light from other directions and confused the movement of ants.
Polarised light This is light that has passed through a filter such as the Earth’s atmosphere. Depending on how high in the sky the sun is more or less polarised light gets through. When the sun is high in the sky (around midday) very little polarisation occurs. But just after sunrise and just before sunset lots of polarised light reaches the Earth’s surface. (See your local physicist for more detail). It is thought that some species, for example homing pigeons can detect polarised light and as a result can tell the position of the sun even on days when it is obscured by cloud cover.
Von Frisch
(ultimate anorak when it comes to bees, much more on him later when we do
communication) believes that bees use polarised light to indicate position
of nectar sources in relation to the hive. It is necessary for some blue
sky to be visible for this to be possible! He confused bees by passing UV
light through a filter (creating polarisation). This caused the bees to
alter the direction of their infamous bee dances!
Clock-shifting As I’ve already pointed out animals rely on their biological rhythms to navigate using the sun. These experiments are designed to alter the animals’ rhythms, confuse them into thinking it’s a different time of day, and observing what effect this has on their navigation. Walcott (1972) and Keeton (1974) altered the body clocks of seagulls and pigeons respectively. The birds are kept under artificial lighting, for example lights come on at midnight and go off at midday, about six hours earlier than the natural conditions outside. As a result when the birds are released their clocks are six hours out. This equates to 90 degrees of sun movement. As a result when the birds are transported away from their loft and released hundreds of miles away the set off in the wrong direction, e.g. heading north instead of east! However, they still find their way home eventually suggesting that the sun is used as a first resort, but that if this fails they have other methods that they can rely on.
How birds use the sun to navigate Two methods have been suggested. The map-compass hypothesis is the method already outlined above. Animals consider the position of the sun from east to west in the sky. So if they fly towards the sun in the evening they are going in a westerly direction etc. The sun-arc hypothesis is more complex because it suggests that species also consider the height of the sun in the sky. For this to work the bird etc. must learn the position of the sun (height and position east to west) for each time of day in its home location. When moved away from home it is able to determine where it is for example if the sun is lower in the sky than expected it realises that it is further north than home etc. Grier & Burk (1992) showed that birds only adjust for position east to west, not height of sun in the sky, suggesting that the simpler map-compass method is used. Stars Bellrose (1958) attached spotlights to the feet of mallards so he could track them at night. He found that when the sky was clear and the stars visible that the birds would all fly in the same direction. However, when the sky was overcast birds would fly aimlessly. In the Northern hemisphere it appears to be the Plough (or big Dipper for our American Cousins*) that is used as a direction finder. The Plough is adjacent to the Pole star and rotates around it. As a result it is always in the North.
Emlen (1975) highlighted the importance of the plough by rearing young buntings in a planetarium under an artificial night’s sky. In the wild the birds migrate south in autumn and return home, in a northerly direction, in the spring. In the planetarium the young birds appear to imprint on the Plough and fly away from this (South) in autumn and towards it (North) in the spring. Emlen placed ink pads and blotting paper around the bird’s cages to record their foot prints and gauge which way they were trying to fly. In a follow up experiment Emlen imprinted the birds on the star Betelgeuse (pronounced ‘beetlejuice) in the constellation of Orion. When the birds were released into the wild they flew in the opposite direction to the one expected. Crucially what this does show is that although birds appear to have an innate ability to imprint on stars for the purposes of navigation, there is still an element of learning involved. *Piece of trivia: President Abraham Lincoln was watching the play ‘Our American Cousin’ at the Ford Theatre in Washington DC when he was assassinated!
Magnetic fields
As we have seen birds may be temporarily disorientated by clock shifting and by overcast skies etc., but they seem to have a back up, fail safe mechanism for navigating if all other methods fail. Keeton (1969) and others have fitted magnets or Helmoltz coils (electromagnets) to the heads of birds such as pigeons or laughing gulls and found that they become disorientated. However, this only happened on overcast days when the position of the sun could not be judged. Their conclusion is that birds use the sun as their first choice but if this fails they use magnetic fields. Gould (1982) reported that pigeons can become disorientated by magnetic storms and there have been reported cases of many homing pigeons being lost when racing during such storms. Emlen (1976), in an experiment similar to his planetarium study, placed young buntings in cages in a shed. The shed had a large Helmoltz coil fitted to the roof. Using this, Emlen was able to vary the direction of the magnetic field inside the shed. In the spring young birds would normally jump in a Northerly direction mimicking their migration north. However, when Emlen adjusted the magnetic field by 120 degrees he found that the birds started to jump in a south easterly direction instead.
How animals detect magnetic fields The mechanism is not clearly understood. Beason (1989) found magnetite, a compound of iron, in the brain of a bird called the bobolink. When magnetic fields around the bobolink were altered using magnets, electrical activity was recorded in these brain areas. Others however, remain sceptical. Wiltscko & Wiltschko (1988) suggest that it may be possible for the Earth’s magnetic fields to be detected within the visual system of some species. As with animal memory, evaluation marks are tricky for this topic. Think of what the evidence suggests and emphasise that animals seem to use different techniques in different circumstances. Over long distances the sun appears to be the first choice for most species. However, at night this is obviously not possible so the stars are used (especially the Pole star and Plough). If conditions are overcast and sun and stars are not visible then at least some species appear to have the ability to use magnetic fields. Although these methods are good for covering long distances they are not precise enough to get an animal to its exact location. Having got close to their destination precise homing can be achieved using methods such as visual landmarks or smells or both. Other evaluation marks can be earned by considering the possible roles played by innate factors and learning and by criticising and/or comparing studies.
Animal Communication
Introduction All animals communicate, either with members of their own species or across species. Communication can act as a warning, a mating call or for a number of other purposes. However, does simple communication of this type constitute language? Hockett, and others have laid down criteria that distinguish language from mere communication, for example a true language is able to communicate ideas about events in the past or future, so called displacement. This section looks at:
1.Natural Animal Communication What is communication? Put simply it is a two way process that allows a message to be sent and received. Obviously for the message to be useful to both sender and receiver, the signal sent must have the same meaning for both of them. Think of the confusion an Englishman in New York might cause by asking for a ‘fag!’ It also seems safe to assume that communication (or signalling) of this sort must confer some evolutionary advantage on species as a whole, otherwise it would not have survived as a pattern of behaviour. Individuals that use signals would have been more likely to survive and prosper and pass their genetic material into the next generation. However, there are examples when signals like these can be of disadvantage to either the sender or receiver. (see details on eaves dropping and dishonest signals). Some possible advantages of signals:
members of the species of an approaching predator. (Ververt monkey).
of members of the opposite sex. (Peacock's tail).
submissive signals that settle most disputes without recourse to physical aggression. (Arched back of a domestic cat).
of food locations. (Waggledance of the honeybee).
1. Honest signals These usually involve ritualised forms of normal gestures to provide a message with unmistakeable meaning. For example the cowering of a dog to represent submission or fear. Many mating signals also fit into this category. Ritualisation: Most honest signals are exaggerated forms of animal behaviour. For example the arching of a cat or dogs back to exaggerate its height is used as a sign of dominance to ward off would be aggressors. Similarly the cowering posture that reduces their size is used to signal an individual’s submissive nature. Used together these two signals can avoid costly and aggressive encounters. Ritualised signals tend to be highly conspicuous (and may involve lots of noise or elaborate movements). This ensures that the signals are noticed! They also tend to be very stereotyped ensuring that they are not misinterpreted. In some cases this can ensure that an animal does not waste its time (and all street cred’) by attempting to mate with the wrong species!!! 2.Dishonest signals These aim to deceive and put the receiver at a disadvantage. For example smaller male cricket frogs lower the tone of their croak to make themselves sound larger. (A ploy used by some men in male dominated industries to make themselves appear more macho!). The young cuckoo signalling hunger and deceiving its adoptive parent into giving it food. 3. Eaves-dropping When a predator picks up signals that are not meant for it. For example if a signal, intended to pick up a mate, is intercepted by a predator that then uses the information to locate the signaller. The female bark beetle (all life is here!), releases a scent to attract males to her tree. However, other females intercept the signal and close in on the sender and take advantage of the attracted males she is attracting!
Channels of communication This refers to the sensual (broadest sense) methods that a species can use, such as visual, auditory, tactile etc. Each has its advantages and disadvantages and below is a list of these with specific animal examples. Visual It is estimated that about 70% (some estimates put it higher) of human spoken language is actually conveyed visually in the form of body language. In the animal world visual messages are widely used in courtship especially in birds and fish. The male stickleback will perform ‘zig-zag’ dance that can stimulate a female into releasing her eggs into the water for the male to fertilise. Robins will attack red feathers nailed to a tree but will completely ignore a whole stuffed robin that does not possess red colouration (Lack 1943).
Channels of Communication
Auditory (sounds) As humans (speaking for the majority of us now), this is the channel we most associate with language and communication. Many other species, most notably birds, also make good use of sounds in communication and signalling. Sounds can be varied in a number of ways: · Pitch (or tone): female toads apparently prefer males with a deep ‘voice’ as they suggest larger males (obviously no one has told them that size doesn’t matter Ed). · Volume: clearly a louder signal will have more impact and travel further. · Sequence: the order in which the sounds are deployed, crucial in human language but also in other species such as crickets. Many species vary all three to good effect to alter the meaning of their call. A good example of this is the vervet monkey that we will look at in more detail later.
Olfactory (smells) Pheromones (chemical messengers) are usually the method of first choice! Releaser pheromones usually have a short term effect bringing about a sudden change in behaviour, for example attracting male moths to a female releaser. Primer pheromones usually have a longer term effect and may alter the physiology of the receiver. It is common for many species such as domestic cats to mark their territory with scent. This is achieved by the pheromones in their urine. A few statistics: each antenna of the male silk worm moth has 10,000 hairs that it uses to detect female pheromones. Just a few molecules can change the behaviour of the moth. Simmons (1990) found that smell can be crucial in preventing accidental incestuous breeding. Female crickets showed a preference for more unrelated males as evidenced by their pheromone. Attachments between mother and offspring may also be mediated by smell. Farmers will cover an orphaned lamb in the afterbirth of another newly born lamb to persuade the mother to adopt the orphan. (Once saw this being done… then went home and had a neck of lamb casserole that I’d made earlier!)
What is language? Psychologists as well as linguists have problems in defining ‘language,’ both finding it easier and more useful to identify the different properties that characterise language. The most widely used set of criteria are those devised by linguist Charles Hockett who has compared human languages with other forms of communication. Hockett’s criteria: Symbolic or semanticity: the method of communication uses symbols that have a shared meaning between all those members of the species using it. In human terms, the word ‘tree’ in English, has a shared meaning between all people around the world that speak our language. Syntax: the use of these symbols requires rules, for example in English the adjective usually goes before the noun ‘the red book’ as opposed to ‘the book red.’ Those that do French will be aware that this is not always the case in French. Some adjectives are placed after the noun. Arbitrariness: the symbols used bear no resemblance to the action or object that they are representing. The word ‘car’ is arbitrary since it looks or sounds nothing like the object that it represents. The waggledance of the bee however is not arbitrary since the direction of the dance represents the direction of the nectar and the speed of the dance reflects the distance. Specialisation: the sounds created have no other function other than what they are representing. For example the panting of a dog has a biological purpose. A dog squealing because of pain does not do so to communicate the pain but because it is in pain. Displacement: the language can communicate about actions, objects or emotions that are not present or visible at that moment. For example the waggledance shows displacement because it refers to nectar not visible to the dancer. Human languages can communicate ideas about actions that occurred yesterday or may happen tomorrow, so are not impinging on the individual at that moment. Most animal communication refers to immediate environmental stimuli such as the presence of a predator. Cultural transmission: the method of communication is passed from one generation to the next by a process of teaching. This appears to be the case with some birdsong but is not true of the waggledance which is innate and present from birth. Generativity or productivity: the number of utterances possible using the language is infinite. Using the English language I could say ‘Me and Kylie popped down the Sugarloaf for a pint of Abbot and a prawn vindaloo.’ The chances are nobody has ever said that before. Most methods of animal communication have nothing like that level of flexibility. The calls of most species are very limited in scope. Prevarication: the language can be used to tell lies or jokes. Discreteness: the language combines smaller units (e.g. words) to create meaning (e.g. sentences). Interchangeability: an individual can both send and receive messages. Hockett’s first criterion, not mentioned above, is that the language should be vocal or auditory. I leave this ‘til last since it not only rules out the waggledance, but would appear to relegate nearly all attempts of teaching apes and cetaceans to mere communication. It would also rule out sign language!!!
Does natural animal communication constitute language? What follows is a brief description of various natural signalling systems and a consideration of whether or not they fulfil Hockett's criteria. 1. Birds Birds make most use of the auditory channel, so called birdsong. This is often used in conjunction with other channels such as visual signalling. Hunter and Krebs (1979) found that the nature of their song relates to their environment. · In open spaces birds use a wider range of frequencies and repeat notes and sequences of sound faster. · In dense forests they use lower frequencies. Wiley & Richards (1978) attributed this to communication of the message with minimum distortion. In forests trees cause reverberations. Lower pitched sounds are less likely to be disrupted. In open spaces the greatest risk is from strong winds. High-pitched sounds, quickly repeated are less likely to be affected.
Is birdsong innate or learned? (Easy evaluation marks to be had here). Crickets reared in isolation (so they have never heard other crickets sing), still sing themselves. Obviously, crickets are not birds, but this suggests that their song is innate. However, higher species, such as sparrows, when reared in isolation between 8 and 90 days old, fail to pick up birdsong, suggesting that it is learned, or as it applies to Hockett, ‘culturally transmitted.’ Note. It is possible for birds reared like this to pick up the song of related species. The conclusion, therefore is, that the ability to sing is innate, the nature of their song is learned.
Is it language? No. 2. Honeybee The dances of the honeybee were studied by von Frisch over a period of many years. Two distinct types of dance were observed: 1. The Round dance. (Indicating nectar within an 80m radius). The returning bee dances in a circle, as the name suggests. The other bees then fly off and search nearby. This dance gives no indication of direction. 2. The Waggledance. (Indicating nectar more than 80m away). The returning bee performs a more elaborate dance that indicates approximate distance, and crucially direction. a. Direction is indicated by the angle at which the dance is performed. The dance comprises of a figure of eight. The straight stretch in the middle is the relevant bit. If this is vertical on the wall of the hive it informs the others that the nectar is towards the sun. Dancing downwards would mean fly away from the sun etc. b. Distance is indicated by the energy put into the dance: i. Number of times the bee completes the cycle ii. Number of waggles iii. Amount of noise made. The greater the energy expenditure the nearer the nectar is to the hive. Remember that the hive is dark inside so visibility is minimal. The observing bees therefore follow the dancer to assess direction and the dancer herself regurgitates some of the nectar as an additional clue. Subsequent research has backed up von Frisch’s early work on the complex nature of the dance. The method of communication has some degree of flexibility. For example the bees only dance on about 10% of occasions when the source they have found is particularly plentiful or if the find satisfies a particular need of the hive. The receivers don’t always act on the information. The Goulds sat in a boat in the middle of a lake and provided nectar to passing bees. These returned to the hive and performed the appropriate dance communicating the location of the find. However, the others did not act upon the information. The Goulds assumed this was due to the bees having a mental or cognitive map of their immediate environment. They would have realised that the dance was indicating the presence of nectar in the middle of water. Since this would normally be impossible the receivers assume a mistake has been made and ignore the message.
Is it language? No. Additional points Bee dances are not productive in that the message is always communicating the same thing, no new subjects are incorporated. Also the language does not demonstrate reflexive in that the bees are unable to communicate anything about themselves. 3. Whales Whales communicate via song and this is often compared to the songs of birds. Typically a song lasts about 30 minutes and comprises long, slow notes. Songs are split into themes and themes into phrases. Finally each phrase comprises notes. Whale species average about six themes, but they do change over time. All the whales in a given area sing the same song but this does change during the course of a season. At the start of the next singing season the whales sing the same song as they were singing at the end of the previous season. The meaning of the songs is difficult to interpret and a number of suggestions have been put forward. Some have suggested that given the huge brain of the whale its songs must have complex meanings, but this appears not to be the case. 1. Mating call. Winn & Winn (1985), along with others, have reported that only males sing suggesting a mating role for the songs, seeking to attract females. They suggest that a build up of androgen (male hormone) triggers the call. Tyack (1981) watched singers pursue non singers and then engage in courtship type behaviour, again suggesting a mating role. 2. Warding off other males. Winn & Winn (1985) suggest that the lower frequency notes of the songs may be an attempt by males to keep other males at bay. Typically songs combine notes of different pitch, so the songs could be conveying different messages. 3. Feeding behaviour. (D’Vincent 1985) suggest songs appear to play a vital role in all manner of social behaviours including feeding. 4. Surfacing. Whales need to surface at regular intervals, Winn et al (1979) report a ‘ratcheting sound’ immediately prior to surfacing and this has enabled scientists to predict when whales will surface.
It is worth remembering that the song of the humpback whale will save the earth in the 23rd century! (Information published courtesy of the producers of Star Trek).
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